Is SolFS subject to fragmentation?
Fragmentation was a problem on physical HDD disks with moving heads: to read and write sectors the HDD has to reposition heads and this slows down reading and writing. On modern multicore processors with a number of files being read and written in parallel fragmentation is not that influential, as it was in old good MS DOS days. Also, fragmentation is not applicable to flash drives (SSD, flash cards etc).
In case of SolFS the volume is a file on the regular disk (it's usually HDD, SSD or flash card), so having or not having the data written sequentially in SolFS storage doesn't matter because the storage file is often fragmented as well. If SolFS storage is stored remotely or in memory, sequence of pages doesn't matter at all as well.
Due to the above we think that fragmentation is not an issue for SolFS.